Primary cell with permanganate



Oct. 30, 1951 s, RUBEN K Re. 23,427

PRIMARY CELLA WITH PERMANGANATE DEPOLARzER original Filed March 14, 1945 AMALzm/c zuvc Powpfk VOL T5 o Ee In 5 745202550554045 sossenssm zssosssqgsmofosmusmfzs INVENTOR BY Samuel Fue ATTORNEY Rcued Oct. 30, 1951 23,421 ramer caLLwrrn rmANGANA'rE naromrzan samuel animi. New mme. N. Y.

Original No. 2,462,998, dated March 1, 1949, Serial No. 582,594, March 14, 1945. Application tor reissue February 21, 1950, Serial No. 145,520

28 Claims. (Cl. 13B-407) llatterencbledlnheavy brackets [lappearsintheorlglnalpatentbutformsno partoftlils reissue speciilcation; matter printed in italics indicates the additions made by reissue.

This invention relates to primary cells of the alkaline type. In its preferred embodiment it relates to sealed dry type alkaline primary cells.

An object of the invention is to improve primary cells and theelectrodes thereof.

The present invention contemplates a primary cell embodying a cathode formed of a depolarizer composition using silver or copper permanganate intimately mixed with a conductive material. The invention also contemplates features of cell construction which facilitate effective use of the cathode and other cell materials. Other aspects of the invention will be apparent from the following description taken in conjunction with the accompanying drawing. in which Figure l is a sectional view of a sealed alkaline dry cell embodying features of the invention;

Figure 2 is a bottom view thereof;

Figure 3 is a section of a flat type cell;

Figures 4 and 5 are longitudinal and transverse sections of another cell construction; and

Figure 6 is a graph showing curves of primary cell voltage versus time under load.

The present invention contemplates a primary cell embodying a cathode formed of a depolarizer composition using silver or copper permanganate intimately mixed with a conductive material. The invention also contemplates features of cell construction which facilitate effective use of the cathode and other cell materials. Other aspects of the invention will be apparent from the following description and claims.

Referring to the drawings Figures 1 and 2 show a primary cell comprising a steel cup or container III in the bottom of which is pressed a cathode pellet Il of depolarizer composition.

In the preferred embodiment of the present invention the cathode depolarizer composition l I is an .intimate mixture of silver permanganate and graphite so as to produce an electrically conductive cathode element. In order vto obtain the best results the graphite particles should be finer than the permanganate particles and the two should be intimately mixed or ball milled together so that the permanganate particles are substantially coated with a graphite film. The permanganate should be as pure as possible and finely divided. Microniaed Ceylon graphite (for ex- .nple, Dixon's 200-09 and 200-12) shows superior properties for this purpose. While the proportions of the graphite may be varied over a considerable range the most suitable compositions contain l to 50% graphite and 20 to 30% graphite is preferred, although the specific application of the cell may determine the preferred graphite amount. The composition is compacted to a dense body, a pressure of about 20,000 pounds The preferred barrier consists of one or more porous discs i2 of a non-oxidizable material, preferably ilbrous polystyrene. These may be punched from a 5 mil sheet and then pressed into the cup on top of the depolarizer. Other suitable organic non-oxidizable materials, such as fibrous nylon sheet etc., may be used. Other barriers which are suitable are a pressed disc of magnesium silicate or A magnesium hydroxide powder or a mixture of both, or of ceramic powder. These are pressed into the cup simultaneously with pressing of the depolarize': or as a subsequent operation. It is of advantage to use an inert inorganic barrier or non-oxidizable organic barrier in contact with the permanganate-graphite electrode to avoid surface reduction of the permanganate. Cellophane and dialysis parchment paper, while they can be used, are not quite so desirable for this reason.

The anode assembly for the cell comprises a roll of corrugated zinc foil I4 interleaved with a double layer i5 of polystyrene bre sheet or, in some instances, porous paper. The zinc foil edge extends beyond the fibre layer slightly at one end and the bre layer extends beyond the zinc at the other end of the roll. At least one complete turn of the libre sheet encloses the outermost turn of the zinc at the outside of the roll. An impervious insulating sleeve I6 of polystyrene or paper impregnated with polystyrene or other alkali-resistant insulating material encloses the roll and holds it assembled and insulated from the walls of container. A suitable method of making this anode assembly is shown and described in my copending application Serial No. 513,687, filed December 10, 1943, now Patent No. 2,422,046.

The anode roll is impregnated with an alkaline electrolyte solution and the zinc foil is amai-- gamated with mercury in the same operation. Anode rolls are placed in a flat bottom dish with the zinc end up and the electrolyte is poured into I6 the dish slowly allowing; the electrolyte to be of each roll in contact with the zinc. A suitable proportion of mercury is to 20% of the weight the zinc top to such an extent as to become brittle so that if an excess gas pressure is had after complete use of the depolarizer, any bulging caused by the gas pressure will cause cracks to of the zinc. The dish is then placed in an oven at 60" C. for several hours or until amalgamation of the zinc foil surface is substantially complete.

'I'he rolls are then drained and moderate vac- ,uum applied to remove entrapped gas bubbles.

An impregnated anode in this condition is then placed in the container I0 with the projecting nbre end in contact with the less porous polystyrene discs |2 which absorb some of the electrolyte from the projecting nbre end.

An amalg'amated zinc top disc |1 of pie-pan shape is placed in the mouth oi' the container Il with its depressed center in contact with the projecting zinc foil Il of the anode roll. A neoprene grommet ring I8 encloses the edge of disc |'I and rests on a shoulder |9 formed in the container wall. A ilat steel ring or washer 20 is placed over the grommet and the free edge 2| of the container is turned or spun down over the top of the washer to place the grommet under compression and seal the cell. y

If desired the grommet can be sealed to the surface of the zinc disc with neoprene cement to further insure against electrolyte creepage. A terminal tab 22 is soldered or spot welded to the center of the top disc and then the entire exposed outer zinc surface is sprayed or painted with an air-excluding lacquer 23. such as a mixture of hydrogenated rosin plasticized with mineral oil.

Best performance is obtained from cells having the electrode and spacer elements held together under substantial pressure by the container parts. Thus, it is desirable that the anode roll assembly Il. IS be compressed by as much as 10% or more.

The preferred electrolyte is a solution of potassium hydroxide which has been substantially saturated with zinc oxide by heating in the presence of excess zinc oxide and then iilterlng. A solution containing about 38% KOH and 6.4% ZnO is very satisfactory although the concentration can be varied over a wide range. For most practical applications the KOH amounts to about 20% to 50% of the solution with sunlcient ZnO to saturate the solution. This electrolyte and its advantages are described more fully in my co-pending application Serial No. 486,367, led May l0, 1943, now Patent Number 2,481,539 as well as application Serial No. 513,687 above referred to.

Other electrolytes can be used in the cell, especially where it is intended for use at low temperature and appropriate venting means are used, such as straight solutions of KOH, NaOH or LiOH or mixtures of these.

In some cases it may be necessaryor desirable to provide venting means, which are normally closed but which will relieve gas pressure, should any gas develop after complete use of the depolarizer. One convenient venting arrangement is illustrated in Figures l and 2, which comprises a pair of crossed chisel grooves 24 on the bottom of the container which do not completely penetrate the wall. 'I'he cell is therefore completely sealed but if gas pressure should develop the cross will open up sumciently to permit escape of the gas. Another method is to amalgamate the sealing operation appear and venting takes place through the cracks. Still another method of venting is to use a porous oil impregnated sealing grommet.`

of neoprene or other suitable inert resilient material in a ring shape such as shown at Il. This allows some passage of gas outward through the porous grommet should internal gas pressure develop.

Figure 6 is a graph showing curves of voltage versus time under load obtained with cells of the construction described having depolarizer cathodes of AgMnO4 mixed with 20% micronized graphite; and of CuMnO4 mixed with 20% graphite. The cells hadva diameter of inch and were inch high. The zinc anodes were each formed of 2 mil zinc foil corrugated with 2 mil deep corrugations the corrugated foil strips being inch wide and 36 inches long. The foil is wound up with two 4 mil porous paper spacers a inch wide. 'I'he depolarizer in each case was formed into a pellet and compressed into the bottom oi' the can at 20,000 pounds perl square inch. The AgMnOi-graphite pellet weighed 2.9 grams. 'I'he CuMnOl-graphite pellet weighed 2.1 grams.

'The paper spacers were impregnated with 2.5

grams of electrolyte containing 38% KOH and 6.4% dissolved ZnCh. The barrier I2 consisted of two 5 mil porous polystyrene fibre discs. 'I'he hours under continuous load. Curve 26 is a similar curve for the CuMnO4 cell. The cut-of! voltage was reached after about 42 hours.

The two curves represent continuous initial runs under 111 ohm load until the voltage -dropped to 0.9 volt. If the cells are allowed to recuperate the voltage rises again and further output can be obtained above the cut-on' voltage for several cycles, giving a much longer total run.

The original open circuit voltage of the silver permanganate cells was 1.96 volts and that of the copper permanganate cells 1.94 volts.

Cells made without graphite or other conductive material mixed with the permanganates dropped ot! in voltage to a low value almost as soon as they were connected to a load.

Figure 3 shows a ilat cell construction comprising a shallow steel cup 30 containingv a silver or copper permanganate-graphite depolarizer cathode 3| and a pressed zinc powder anode 32. The depolarizer composition 3| is pressed in the bottom of the container-30 and a barrier disc 33. v

which may be porous polystrene, pure asbestos. pressed glass powder, zinc oxide, magnesium silicate or magnesium hydroxide powder for example, is pressed on top of it. Aninsulating sleeve ring 25 is set on the barrier and against the side wall of the cell. This may be of polystyrene or other alkali-resistant pliant material. One or more porous fibre discs 3l are impregnated l with electrolyte and laid on the barrier inside the sleeve 35. The anode.comprises a disc pressed from iron-free zinc powder which has been amalgamated with 5 to 15% of mercury. It may also be made from zinc granules or pellets which have been amalgamated. Amalgamated zinc top I6 presses against the top of the anode and holds it tightly against fibre disc 34. The top 36 is sealed in the mouth of cup by neoprene grommet 31 which is compressed against it by the enclosing edge of the container.

Figures 4 and 5 illustrate a cylindrical electrode construction in a primary cell embodying other features of the present invention. The deep steel container 4l) has a liner disc 4l of polystyrene on its bottom. Upon this rest a group of concentric cylinders. The outer cylinder 42 is of pressed permanganate-graphite composition and is fitted or pressed rather tightly against the cylindrical can wall.

The anc .le comprises a pressed amalgamated zinc powder cylinder 43 which stands slightly higher than the depolarizer electrode. Between the anode 43 and the depolarizer cathode 42 is a spacer 44 comprising a winding about 40 mils thick of porous polystyrene fibre sheet, or the combination of paper adjacent the anode and polystyrene fibre adjacent the cathode.

Instead of layers of sheet materials, the spacer can be of a compressed absorbent material such as a pressed cylinder of a mixture of magnesium hydroxide and magnesium silicate, polystyrene libres or a ceramic material.

The hollow interior of the anode is filled with a wad or roll 46 of porous polystyrene fibre or paper. The electrolyte is added to this roll and quickly passes through the porous anode and spacer 44 by capillary action and even to some extent into the depolarizer to effect uniform distribution of electrolyte. No excess free flowing electrolyte is allowed to remain. The fibre or paper swells in the electrolyte exerting a pressure against the anode and cathode cylinders. Polystyrene ring disc 49 covers the top of cylinders 42 and 44.

The amalgamated zinc top 41 is pressed against the top end of anode cylinder 43 and is sealed in the mouth of the container by neoprene grommet 48. It will 'be noted that the length of the cell can be varied without changing the ratio of the anode and cathode volumes or surfaces..

During cell operation the electrolyte reacts with the zinc and zinc hydroxide is precipitated on the anode forming a coating thereon. By using an anode of large surface area as set forth in my above mentioned applications the coating never reaches a thickness where it will interfere with useful operation of the cell until the depolarizer has been consumed. For maximum cell life the zinc surface area should be preferably at least 4 square inches per gram of the depolarizer.

The electrolyte is constantly regenerated so that only a small quantity is necessary to the continued functioning of the cell.

The cells described herein are found to have a longer life on intermittent service than on continuous use at the higher drains. They appear to recuperate and return to higher voltage during periods of non-use.

It is of importance in avoiding local action for the zinc used for the anode to Ibe substantially pure. The iron content particularly should be kept low, preferably below .003%. Other metals such as copper and tin should be kept below this proportion.

The barrier layer between the cathode and the anode being electrolyte permeable permits cell operation but substantially prevents migration of compounds from the cathode towards the anode.

The cell contains no free-owing or freely-circulating electrolyte, as a result of keeping the weight ratio of electrolyte to bre between 3:1 and 6:1 in the case where polystyrene fibre is used. This factor further restricts travel of compounds to the anode where they would cause deleterious local action and is one of the most .basic factors necessary for long shelf life.

In relation to the depolarizer the amount of electrolyte within the cell may be about 0.3 gram per gram of depolarizer in the flat and cylindrical structures and about 0.8 gram electrolyte per gram of depolarizer in the coiled foil anode type.

In the manufacture of the cell it is desirable that the permanganate and graphite be substantially compressed as to produce an electrically conductive mass. An excess of electrolyte is to be avoided. l

There should be only sufficient electrolyte in the spacer to allow conduction and ionic migration but insufficient to allow dissolving of the permanganate by circulation or ow of the electrolyte. If the permanganate isused with a wet or free flow electrolyte construction it would rapidly dissolve and decompose into the electrolyte Yand adequate shelf life would not be possible.

The barrier is of considerable imponce. It should limit circulation of the electroly e and it should have substantially no reducing action on the permanganate, particularly where high temperature operation of the cell is to be encountered.

The use of the more reactive organic materials, such as paper, in contact with the depolarizer is generally to be avoided. The more stable organic materials, such as polystyrene fibre, or inorganic barriers are preferred. While paper can sometimes be used in other parts of the cell, such as for spacing apart the turns of the anode foil, some advantage is gained even here in using a less reactive material.

The permanganates .described in this application as well as the ones described in my prior application Serial No. 575,090, now Patent Number 2,463,316, are the water soluble permanganates. 'I'he combination and arrangement of cell elements described herein makes possible the use of such soluble permanganates in solid form. For example, the use of an electrolyte retaining spacer or barrier layer in contact with the cathode prevents free circulation of the electrolyte which would dissolve and carry away the permanganate but permits the ionic conduction necessary for cell operation, and permits eflicient depolarizer action at the cathode surface.

While specific embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is;

l. A primary cell comprising a zinc anode, a cathode comprising an intimate mixture of a permanganate selected from the group consisting of silver and copper permanganates in solid state and a nely divided conductive material, a porous spacer between said anode and cathode and in contact therewith, and an alkaline electrolyte absorbed in said spacer.

-2. A primary cell comprising a zinc anode, a cathode comprising an intimate mixture of a permanganate selected from the group consisting of silver and copper permanganates and a nely divided conductive material, a porous spacer between said anode and cathode and in contact therewith. and an alkaline electrolyte absorbed in said spacer, said cell being characterized by the sus? absence or any i'reely held in said spacer,

3.Aprlmarycellcomprisingasincanode.a cathode comprising an intimate mixture of graphite and a permanganate of metal selected from the group consisting oi silver and copper. a porous spacer between said anode and cathode and in contact therewith, 'and an alkaline electrolyte absorbed in said spacer. a container for said anode, cathode and electrolyte impregnated spacer, and conductive terminals comprising part oi said container. and connected respectively to said anode and cathode, and sealing means insulating said terminals from each other and sealing said cell.

4. A primary cell comprising a zinc anode. a cathode comprising solid permanganate oi a metal selected from the group consisting oi silver and copper, and a conductive material mixed therewith, a porous spacer between said anode and cathode and in contact therewith. at least part of said spacer comprising porous substantially inert organic fibre. and an alkaline electrolyte absorbed in said spacer, said electrolyte in said nbre being present in proportions between 3 and 5 ltimes the weight of said fibre. y

5. A primary cell comprising a zinc anode. a cathode comprising solid permanganate intimately mixed with graphite, said pete being selected from the group consisting of silver and copper permanganates, a porous spacer between* said anode and cathode and in contact therewith. and an electrolyte comprising an alkaline solution impregnating said spacer.

6. A primary cell comprising a zinc anode. a cathode comprising solid permanganate intimately mixed with graphite or a nner particle size than that of said permanganate, d permanganate4 being selected from the gro p consisting oi silver and copper permanganates. a porous spacer between said anode and cathode and in contact therewith, and an electrolyte comprising an a1- kaline solution impregnating said spacer. said electrolyte being substantially saturated with alkali metal zincateand said anode having a large surface area.

7. A primary cell comprising a zinc anode. a cathode comprising solid permanganate oi metal selected from the group consisting of silver and copper intimately mixed with graphite of a nner particle size than that of said permanganate, a porous spacer between said anode and cathode and in contact therewith, and an electrolyte comprising an alkaline solution impregnating said spacer, said electrolyte being substantially saturated with Yalkali metal zincate and said anode having a large surface area, a hermetically sealed container having terminals connected to said anode and cathode respectively, enclomng Y said anode, cathode andelectrolyte impregnated spacer, and said cell being further characterized by the absence of any freely owing electrolyte therein.

8. A primary cell comprising a zinc anode, a cathode comprising an intimate mixture oi' Isolid permanganate oi' metal selected from the group consisting of silver and copper and a conductive material, a porous spacer between said anode and cathode and in contact therewith, and an electrolyte comprising an alkaline solution impregnating said spacer, said spacer including a porous barrier of ionically permeable non-reactive material which is inert to said electrolyte and to said permanganate covering the electrolyteengaging surface or said cathode.

10. A primary cell comprising a zine anode V of large surface area, a cathode comprising an intimate mixture of permanganate oi' an element -selected from the group consisting of silver and copper. and finely-divided graphite, a porous spacer interposed between said anode and cathode and in contact therewith. said spacer comprising a barrier layer of semi-permeable material inert to said electrolyte and te said permanganate covering the electrolyte-engaging suriace of said cathode and a layer of porous paper between said barrier layer and said anode. and an electrolyte impregnating said spacer comprising a solution oi' potassium hydroxide substantially saturated with dissolved zinc oxide.

11. A primary cell comprising a cylindrical cathode formed of an intimate mixture of a permanganate o! an element selected from the -group consisting of silver and copper, and a ilnelyfdivided conductive material, a cylindrical anode spaced within said cathode and substantially concentric therewith formed oi a pressedcylinder oi amalgamated zinc powder, a

v porous spacer between said anode and cathode.

saidvspacer and anode being impregnated with an alkaline electrolyte.

12. An electrode for alkaline primary cells comprising a solid permanganate of an element selected from the group consisting oi silver and 0099er.

13. A cathode depolarizer element for alkaline primary cells comprising a solid permanganate of a metal selected from the group 'consisting oi silver and copper.

14. An electrode for primary cells comprising a substantially non-electrically conductive solid silver permanganate mixed with a conductive material.

15. A primary cell containing a cathode comprising a solid silver permanganate. an anode comprising zinc. and an alkaline electrolyte.

16. A cathode depolarizer element for alkaline dry cells comprising a mixture of crystals oi a permanganate of an element selected from the group consisting oi silver and copper, and graphite compressed into an electrically conductive body.

17. A primary cell comprising a zinc anode, an alkaline electrolyte, and a cathode comprising solid silver permanganate, a barrier in contact with said permanganate and interposed between it and said anode, said barrierl permitting ionic conduction therethrough, said barrier being substantially unreactive with said permanganate.

18. In a primary cell, a silver permanganate cathode, an anode, an electrolyte absorbent no nreactive spacer and an inert porous barrier member in contact with said permanganate and said non-reactive spacer, and an electrolyte in said spacer.

19. A Primary cell comprising an amalgamated zinc anode. a cathode comprising a conductive material mixed with a permanganate of metal selected 'from the group consisting oi' silver and copper, a body ot alkaline electrolyte between said anode and cathodev in contact therewith,

and a layer of porous material substantially inert to said permanganate covering the electrolyte-engaging surface of said cathode.

20. A primary cell comprising an anode, a cathode formed of a permanganate of a metal selected from the group consisting ot silver and copper, and an electrolyte in contact therewith which is capable o! generating a current by reaction therewith.

21. A dry cell comprising a metal cup, a layer of insulation on the bottom surface of said cup, a cylindrical cathode lining the circumferential inside wall of said cup and in contact therewith, a cylindrical anode comprising amalgamated zinc spaced within said cathode having one of its ends resting on said' layer of insulation and having its other end extending beyond the corresponding end of said cylindrical cathode, a porous spacer between said anode and cathode impregnated with electrolyte, said spacer including a barrier of ionically permeable materialy having such porosity as to substantially prevent the migration of compounds from the cathode toward the anode, and a metal closure for said cell, the inside surface of which has an amalgam layer, said inside surface of the closure being in contact with the top of said anode cylinder and holding the anode cylinder under compression between said inside surface and said layer of insulation.

22. The cell described in claim 21 characterized in that the metal cup comprises steel.

23. A dry cell comprising a metal cup, a disc of insulating material in the bottom of said cup, an open-ended cylindrical cathode having one end resting on said disc and having its circumferential surface in contact with the corresponding inner surface of said cup, an open-ended cylindrical anode comprising amalgamated zinc spaced within said cathode having one end resting on said disc and having its other end extending beyond the corresponding end of said cylindrical cathode, a porous spacer between said anode and cathode impregnated with electrolyte, said spacer including a barrier of ionically permeable material having such porosity as to substantially prevent the migration of compounds from the cathode toward the anode, and a metal closure for and insulated from said cup having its inner surface in pressure contact with an end of said anode but clearing the corresponding end of said cathode thereby holding said anode under compression.

24. A dry cell comprising-a metal cup, a disc of insulating material in the bottom of said cup, an open-ended cylindrical cathode having one end resting on said disc and having its circumferential surface in contact with the corresponding inner surface of said cup, an open-ended cylindrical anode comprising amalgamated zinc spaced within said cathode having one end resting on said disc and having its other end extending beyond the corresponding en'd of said cylindrical cathode, a porous spacer betwen said anode and cathode impregnated with electrolyte, said spacer including a barrier of ionically permeable material having such porosity as to substantially prevent the migration of compounds from the cathode toward the anode, a metal closure insulatedly mounted in the opening of said cup and having its inner surface in pressure contact with the other end of said cylindrical anode 10 thereby holding said anode under compression. and an annular member of insulating material interposed between the other end of said cylindrical cathode and the inner surface of said metal closure.

25. A dry cell comprising a metal cup, a disc of insulating material in the bottom of said cup,- a cylindrical cathode lining the inside wall of said cup and in contact therewith, a cylindrical anode spaced within said cathode and comprising' amalgamated zinc having its bottom end resting on said disc and having its top end eatendi'ng beyond the corresponding end of said cylindrical cathode, a porous spacer between said anode and cathode, impregnated with electrolyte, said spacer including a barrier of ionically permeable material having such porosity as to substantially prevent the migration Vof compounds from the cathode toward the anode, and a metal closure for said cup in contact with the top of said anode cylinder and spaced from the cup by an insulatingmember, said closure holding said anode under compression, and said metal cup being crimped against said insulating member so as to provide an air-tight seal for said cell.

26. A dry cell comprising a steel cup, a disc of insulating material in the bottom of said cup, a cylindrical depolarizing cathode lining the inside wall of said cup and in contact therewith, a cylindrical anode spaced therewithin, said anode comprising a pressed cylinder of amalgamated zinc powder having its bottom end resting on said disc and its top end extending beyond the corresponding end of said cathode, a porous spacer between said anode and cathode impregnated with electrolyte, that section of the spacer in contact with the cathode comprising an electrolyte permeable barrier substantially preventing migration of compounds from the cathode toward the anode and that section of the spacer in contact with the anode comprising a more porous material, and a metal closure for and insulated from said cup having its inner surface in pressure contact with the top end of the anode but clearing the top end of the cathode thereby holding said anode under compression.

27. A dry cell comprising a cathodeI terminal cup, an open-ended cylindrical cathode in circumferential contact with the inner surface of said cup, an open-ended cylindrical anode comprising amalgamated zinc within and spaced from said cathode, porous material substantially filling out the interspace between cathode and anode and the interior of the anode, an electrolyte absorbed in said porous material in an amount sufficient to cause thorough impregnation thereof but insufficient to cause the presence of free-flowing electrolyte within the cell, an anode terminal member having a surface in pressure contact with an end of the anode, and an insulating sealing member interposed and locked between cooperating marginal portions of said terminal cup and member, the height of said anode being so determined with respect to the height of said cathode as to have the anode terminal member holding the anode under compression while clearing the top of said cathode.

28. A dry cell comprising a cathode terminal cup, an open-ended cylindrical cathode in circumferential contact with the inner surface of said cup, an open-ended cylindrical anode within and spaced from said cathode, porous material substantially filling out the interspace between cathode and anode, an electrolyte absorbed in said porous material in an amount sulcient to l1' cause thorough impregnation thereof but insumcient to cause the Presence of free-flowing electrolgte within the cell, an anode terminal member having a surface in pressure contact with an end ol said anode, a lager of insulation interposed between said anode terminal member and the corresponding end of said cathode, a lager o! insulation interposed between the bottom surface of said cathode terminal cup and the corresponding end of said anode. and an insulatioe grommet locked between marginal portions of said terminal cup and member and delning therewith a sealed enclosure for the cell, the height of said anode being so determined with respect to the height of said cathode as to have the anode terminal member holding the anode cnder compression while clearing the top of said Kathode.

SAMUEL RUBEN.

l2 :immens mlm The following references nre oi' record in the ville o! this patent or the original patent:

UNII'ED STATES PATENTS Great Bl'ltin I- May 30, 1921 

